1. Field of the Invention
The present invention relates to a transistor provided with an amplifying function and a switching function, and to an integrated circuit using the transistor.
2. Related Background Art
Transistors are roughly classified into two types: a bipolar transistor that operates with actions of carriers of both an electron and a hole; and a unipolar transistor that operates with an action of a carrier of either an electron or a hole.
For example, as to a field effect transistor, a voltage is applied to a semiconductor through a gate electrode through a gate insulating film to induce charge in an interface between the gate insulating film and the semiconductor, thereby forming an inversion layer (channel) on a surface of the semiconductor, and thus, electrical conduction is established between a source and a drain. That is, the resistance of the semiconductor is changed due to a gate voltage to thereby change a current that flows between the source and the drain.
As described above, the field effect transistor is made to operate by making the Fermi level of the semiconductor fluctuate due to the gate voltage. Thus, when the voltage applied to the gate electrode fluctuates, the current that flows through the transistor inevitably fluctuates under the operation principle.
Further, when the field effect transistor is in a conductive state (on state), an electric field perpendicular to a channel length direction (moving direction of carriers) is formed in the channel due to the gate voltage. However, the electric field in such a perpendicular direction is one of serious causes of hot carrier injection to the gate insulating film.
When injected into the gate insulating film, hot carriers are trapped by the gate insulating film to form a trapping level, or disconnect bonding of the interface between the gate insulating film and the semiconductor layer to form an interface level, which causes fluctuation in a threshold voltage of the transistor. When the threshold voltage fluctuates, for example, a timing of switching of the transistor varies, or a drain current fluctuates, which becomes a cause of malfunction of a circuit.